Take this response not a a negative but a warning- I personally back in the 80's used the deep substrate bed system within the tank. At that time the recommendations by many were to have a 1" area of water "dead space" at the bottom, with 1" of course substrate (crushed coral) with 2" of sand on top- the bottom dead space was accomplished by using 1" thick acryllic blocks to suspend an egg crate open fluor. light panel- on top of the panel to prevent the sustrate from falling through was a layer of fiberglass screen door mesh which was also put between the course and sand layer.
WARNING- after much success for over 5 years with this system, one morning everthing was lost and the water was like soup. Rationale- the deep substrate bed acts like a sponge for waste and contaminents in the tank. If you do use a deep substrate system, make sure you have many inverts / sand sifters that will turn over the sand as much as possible.
Since the late 80's to now, I have adopted the exact converse of a deep sand bed-
All live rock is suspended on smaller pieces of rock that sit directly on top of the glass bottom of the tank- I only put live sand 1" deep along the front viewing areas and not across the entire bottom of the tank- in a 100Gal tank only use 10lbs. of sand.
The only filtration that is used is the sponges in the overflow and bio balls in the chamber of the trickle filter and filter cloth at the opening from the sump to the pump.
A must for this type of open system is the best protein skimmer that you can afford along with a UV sterilizer.
View photos of 175 and 92 on site to see how successful this system has been!
Chris
